Automatic choke control for internal-combustion engines



April 10, 1951 w. E. ARMSTRONG 2,548,334 AUTOMATIC cHoKE coNTRoL FOR INTERNAL-comus'rrow ENGINES Filed March 17, 1947 lPatented Apr. 10, 1951 AUTOMATIC cHoKE CONTROL FOR INTERNAL-COMBUSTION ENGINES WernervE. Armstrong, Milwaukee, Wis., assigner to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Delaware ApplicationV March 17, 1947, Serial No. 735,150

Y -7 Claims.

This invention relates rto automatic choke controls for internal combustion engines, and refers more particularly to Va choke control for use on small portable internal combustion engines. Automatic choke controls of this type are Yespecially desirableon remotely controlled engines, and those which are started and stopped automatically as in lighting plants, pumping systems and the like. When equipped with the automatic choke control of this invention, such engines may be started at any temperature.

While automatic chokes per se are not broadly new all previous choke controls have been rather complicated and not too reliable. It is, therefore, an object of this invention to provide an automatic choke control of the character described which is simple in construction and operation, and which will function reliably under all conditions of use.

More specifically it is an object of this invention to provide an automatic choke control wherein the choke remains closed or partially closed during cranking of the engine, to be opened promptly upon the engine attaining speed, but at a rate determined by the engine temperature, and wherein the choke valve is held from closing if the engine is stopped while hot so that if the engine is restarted while still hot, adequate air will be supplied during the cranking operation.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly deiined by the'appended claims', it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one f complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practicalapplication of the principles thereof, and in which:

Figure 1 is a perspective view of a single cylinder portable internal combustion engine illustrating the application of this invention thereto;

Figure 2 is a perspective view of the several parts of the torque motor shown disassembled but in their proper order of assembly; and

Figure 3 is a longitudinal sectional view through the thermostatic torque motor which forms part of the choke control.

Referring now more particularly to the accompanying drawing in which like numerals indicate likeY parts, the numeral 5 designates the cylinder of a small portable internal combustion engine which, as is customary, has a cooling fan 6 operating within a blower housing 1. The fan 6 is preferably cast integrally with the fly-wheel 8 and draws air into the housing 1 through an inlet opening 9 surrounding the adjacent end of the crank shaft I() to discharge the same from the upper end of the housing against the side of the cylinder. There is, thus, a well defined upward stream of air flowing along the side wall II of the blower housing.

This air-stream which may be said to be a function of the engine while in operation, is utilized to apply opening torque to the choke valve I2 of a carburetor I3 mounted adjacent to the side wall I I of the blower housing. The carburetor is, of course, connected with the usual intake manifold I4 to supply a fuel mixture to the cylinder.

The choke valve I2 as is customary is of the butterfly type being mounted upon a shaft I5, the inner end of which protrudes into the blower housing through an appropriate opening in its side wall II. The outer end of this shaft has a weight I6 mounted thereon and so located that the torque applied therebyto the shaft at all times tends to close the choke Valve.

The inner end of the shaft I5 has a thin resilient blade-like air vane Il secured thereto to be positioned in the air-stream flowing along the side wall II of the blower housing. Hence the impact pressure applied on the air vane by this air-stream imparts torque to the shaft I5 in opposition to that imposed thereon by the weight I6 to thus tend to open the choke valve.

The balance of this choke assembly is such that at cranking speeds the impact pressure applied on the air Vane by the air-stream flowing through the blower housing is not suicient to open the choke. As the engine accelerates and the velocity of the air-stream through the blower housing increases the air vane is lifted to apply opening torque to the choke valve which thus opens full if the engine is at running temperature.

However, if the engine was cold when started so that it requires an appreciable time before running temperature is achieved, opening of the choke valve is restrained by means of a thermostatic torque motor indicated generally by the numeral I8. This thermostatic torque motor or thermostat is mounted on the cylinder head to be directly influenced by the heat of the engine. It comprises a bi-metallic helical driving coil I9 surrounding a shaft 20 and enclosed within a tube 2|. The forward end of this driving coil is bent outwardly as at 22 and passed through a slot 22 in the tube 2i so as to be anchored thereto. The other end of the driving coil is bent inwardly as at 23 and passed through a slot 23' in the shaft so as to be drivingly connected therewith. The tube 2i is secured in a housing 24 which in turn is fastened ,to the cylinder 'head by screws 25, and bearings 24 in the opposite ends of the housing support the shaft 2t for rotation on a xed axis.

The direction in which the loi-metallic driving coil i9 is Wound is such that with an increase in ambient temperature, the `coil tends to unwind to impart a clock-wise rotation tto ',theshaft 2i) as viewed in Figure l. The limits of such oscillation that can be imparted to the shafts are dened by a stop 26 fixed with respect to the shaft 2S and operating in an arcuate cut-out 21 in the forward end of the tube 2l. The col- ;lision oftthestopi witinthe ends rof thsfarcuate cut-,out defines the limits v'of the :oscillation of the shaft 25.

Alever 2S fixed to the ,outer-end of the shaft it iis connected with the `choke Valve through `a .1ink:29. Theupper end ofthis-link has apivotal connection with :the lever V28. The lower end thereofrhasa lostfmotionconnection with a lever .3i fixed .totthe shaft I5. While-this lostmotion connection can be 4,established in any desirable l manner, it is conveniently obtained by forming yan elongated ,':loopp32 .on the-.end Vofithe Vlink to receive va headed 1pin,33 xed to the lever 3L The :adjustment vof the partsfis :such that un operation thetorqueY motor l:orthermostat re- L strainsthe openingof the choke valvein'response tto air :pressure on the Yvane i1 .until the .engine reaches `its :normal .running temperature. .At this time, the driving coil I9 of the .thermostat will have lifted the connecting link far enough to Yenable complete opening of the choke valve. The opening of the choke thus takes place gradually and in step with the rising .engine temperature.

Attention is directed to the fact that inasmuch as 'the air vane Il is a thin resilient blade, `it will yield and Ahe bent or exed by the air pressure applied thereto, before it will force the temperature sensitive bimetal element i9 vinto a permanent set.

In theeventithe engine is shut down when hot, Vthe thermostatie torque motor or thermostat, acting through its lost motion connection with the choke valve, holds the choke `valve against closing. Thus if 4the engine is Yrestarted while still vhot, a proper fuel mixture will be assured. As the engine cools down the `thermostat automatically allows the choke valve tto be closed by `gravity for cold starting.

From the foregoing :description taken in connection with the accompanying drawing, vit will 'be readilyapparent that this 'invention provides a simple and reliable automatic choke control especially well adapted for'use'on small portable internal combustion engines requiring either remote or automatic operation.

What I claim as my invention is:

1. In an internal combustion engine having a carburetor with a choke valve biased to-closed position, and a fan 'for inducing an air stream proportional 'invelocityto the speed of the engine, the combination of an air vane mounted in Ysaid stream of air to be actuated thereby; a connection betweenthe air Vane and the `choke valve `:whereby response of the vane Vto the impact pres- 4 sure of the air stream as the engine comes up to speed applies opening force to the choke valve; a thermostatl mounted to be influenced by the heat of the engine; and a connection between the thermostat and the choke valve through which the thermostat controls the opening of the `choke valve lby the ,air vane to make opening thereof consonant with warmingup of the engine.

2, In an internal combustion engine having a carburetor with aV choke valve biased to closed position, and `-a Yfari for inducing an air stream, 4the combination of means drivingly connected `.with .the .choke Vvalve and positioned in the air stream to beactuated thereby in a manner to ap- Aply .opening-.torque on the choke valve; a thermostatmounted to respond to the heat developed Vin the engine; and a lost motion connection ,opening ot .the ,choke valve `by ythe air .stream 1responsive means andthrough which closureof ,the Hchoke `valve Yis limited upon lst-oppingof (the enginewhen hot.

.3. In an internal combustionenginefhaving a .carburetor .with .achoke valve biased to-.close'd ,position, .and .asian for inducing an air..,stream, the combination of: .a thermostatic torque motor mounted to 'be responsive to .theheat -developed in the engine; a,shaftdrivingly,connected.to s aid torque motor for rotation .von .the axis of ,said motor; -a Vlost motion lconnection ,between said shaft .and the chQkevalVe -through which the y 4, .In.an .internal combustion ,enginehavingan `upright cylinder Vand a carburetoriprovided with `a, choke valvemounted alongside the cylinder, .said (engine .also havnga fan operating in .a

vblower housing, the combination of.: ,meanslbiasing -the `Achoke .valve toward/closed position; .-a shaftdrivingly ,connected with .the `choke valve .andprotruding into the .blower-housing; an air` Y vane-secured to the shaft inside the blower hous- .fing ,andso positioned :inlthe streamfof the air V.moving lthrough .said housing ,asp-to apply lopening etorque upon thechoke yalve asthe engine comes up -to speed; a vthermostatic :torquemotor mounted on top `of-gthe cylinder above the car- =bunetor to -be zresponsive ,to vthe heat developed .f .fin fthe engine; :and `a lost,motion connectionbeftweenthe movable element ofthe torque motor and the :choke valve for controlling the openin g fof 'the choke -Valveby .the air 4.vane tand for fholdingithe choke v`,valveiagainstffull closure upon c stoppingnof :the engine after a `predeternriined Yen- ;gine temperaturehasrbeen reached.

,5. In an internal .combustion engine having a cylinderiand fafcarburetor alongside the cylinader, the,.-carburetor thaving a choke valve, .the :combination :of: .a thermostatic torque motor mounted on the `headfof the :cylinder to be inuencedbychezheat:developed in the engine, said torque motor comprising a bi:metallic-.coil; a

cachait `encircled roycsaid :coil .and fconnectedvlto one end thereof so that expansion and contrac- 4tion of the coil transmits rotation to the shaft in opposite directions; a link connecting the shaft with the choke valve so that the position of the choke valve may be controlled by the thermostatic torque motor; and other choke adusting means acting on the choke valve in opposition to said thermostatic torque motor comprising an air vane positioned so that air pressure resulting from operation of the engine controls the opening of said choke valve as the engine comes to speed, and a motion transmitting connection between said air pressure responsive means and the choke valve.

6. In an internal combustion engine having a carburetor with a choke valve, and having means for inducing a iiow of air, the combination of: an air vane movable by said flow of air; means actuated by movemnt of the air vane for adjusting the choke valve; a thermostat having a movable element mounted to be influenced by the heat of the engine; a connection between the movable element of the thermostat and the choke valve whereby the thermostat reacts against the force applied to the choke valve from the air vane and thus controls the adjustment of the choke valve by the air vane; and said air Vane being thin and resilient so as to yield to air pressure thereon before force sufficient to cause a permanent set in the thermostat can be applied to the movable element of the thermostat by the air vane. Y

7. In an internal combustion engine having a cylinder, a fan for inducing a stream of air flowing over the cylinder, and a carburetor alongside the cylinder, the carburetor having a choke valve, the combination of: a thermostatic torque motor mounted on the head of the cylinder to be influenced by the heat developed in the engine; a link connecting the movable element of the torque motor with the choke Valve so that the position of the choke Valve may be controlled by the thermostatic torque motor; and other choke adjusting means acting on the choke valve, said other choke adjusting means including air pressure responsive means positioned to be actuated by pressure of the air stream and motion transmitting means between said air pressure responsive means and the choke valve, said air pressure responsive means being resiliently yieldable to cushion reaction forces on the thermostatic torque motor resulting from air pressure on said air pressure responsive means to thus preclude giving the thermostatic motor a permanent set.

WERNER E. ARMSTRONG.

REFERENCES CITED The following references are of record in the le of this patent:

vUNITED STATES PATENTS Number Name Date 1,551,385 Gordon Aug. 25, 1925 2,098,479 Ammon Nov. 9, 1937 2,362,346 Blake Nov. '7, 1944 

